[JimmyR]

There's a setorientation.sh script in the helper extensions. There are no buttons defined to use it, however.

Spoiler:

#!/bin/sh
# I think this is now creds of Ixtab / Yifan Lu. repacked by Twobob.
SETPROP=/usr/bin/lipc-set-prop
PREFS=/var/local/java/prefs/com.amazon.ebook.framework/prefs

case "$1" in
"L"|"R")
        $SETPROP com.lab126.winmgr orientationLock $1
#        $SETPROP com.lab126.winmgr refreshOnTurn true
        ;;
"U"|"D")
        $SETPROP com.lab126.winmgr orientationLock $1
#        $SETPROP com.lab126.winmgr refreshOnTurn $({ grep onPageTurn $PREFS || echo false ; } | sed 's/.*=//')
        ;;
esac